LOUISVILLE, Ky. — It’s that time of the year again when heat and humidity cause sweltering temperatures across Kentucky and southern Indiana.
You’ve likely heard about the heat index mentioned once or twice as well, but what is that? The heat index is a complex formula, but boiled down, it just means how hot you feel.
It’s not the same as the actual temperature, but rather how meteorologists determine the “feels-like” temperature.
According to the National Weather Service, the heat index is a “measure of how hot it really feels when relative humidity is factored in with the actual air temperature.”
For example, if the air temperature is 96 degrees and the relative humidity is 65%, it’s going to feel like closer to 121 degrees.
The NWS has a heat index calculator you can try out here.
It’s important to note that heat index values are calculated for shady locations, so if a person is exposed to direct sunlight those feels-like temperatures can increase up to 15 degrees, the NWS said.
Why does it feel hotter than it is?
The reason we feel hotter when the humidity rises is because our bodies can’t evaporate sweat effectively since the air is full of water vapor. Sweat is our bodies natural way of cooling off.
“Sweat rests on our skin, unable to evaporate into the air,” Mary Benjamin, M.D., an emergency medicine doctor in Minnesota, told HealthPartners. “As a result, our bodies continue to sweat and sweat – but feel no relief. Ultimately, high humidity throws the body into overdrive to cool itself.”
When does it become too hot?
The heat index becomes dangerous when feels-like temperatures reach 103 to 124 degrees. Extreme heat can cause heat-related illnesses like heat cramps, heat exhaustion and heatstroke with prolonged heat exposure or physical activity.
Remember to limit outdoor activities on hot days, stay hydrated with water or drinks with electrolytes before you feel thirsty, wear loose-fitting and breathable clothing, and take frequent breaks in the air conditioning to stay cool.
If you’re driving with children or pets, be sure to check the back seat every time you leave the vehicle. Temperatures inside of a car can become deadly within minutes during hot weather.
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